lab 2 hysys distillation column.docx

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PROCEDURE .

1.

To undergo an initial setup, click on the ‘Start Menu’ , then select programs  Aspen HYSYS 7.3

2.

The Simulation Basis Manager was appeared after clicking ‘File’  and   and „New -

Case‟ were selected. 3.

The ‘view’   button was clicked to view Component Lists in Master Component List. The list of all the components available in HYSYS Component Library

4.

The desired component for simulation simulation were selected by typing the name name of the component, then pressed ‘enter’ . Then, the tab was closed. Makes sure methanol and water were listed in Master Component list.

5.

ag e r   At S i m u l a t i o n B a s i s M a n ag , the Fluid Packages been selected then the

 button been click at the Current Fluid Packages . ‘add’  button 6.

The Fluid Package: Basis 1 tab was appeared then the ‘SRK’   were selected at the Property Package Selection and click ‘ All Types”.Again in the Simulation Basis Manager, the button ‘enter simulation environment’  were clicked.

7.

From the at Case (Main) tab, the ‘material stream’  was  was selected by clicking to the symbol as the feed stream (1). Then, the condition of the stream was set by inserting the data according to the parameter in the worksheet. The flowrate is 2700kgmol/hr,pressure 5.2 bar and the temperature is 25 0C.The composition of the mole fraction of methanol stream was set by inserting 0.5 and 0.5 for water composition respectively

8.

Still in simulation environment, the ‘splitter’  were  were selected and set according to the connection and parameter in the worksheet. On the ‘connection’  page the following setting were applied; inlet: feed 1 (stream 1), outlet: 2 (stream 2):.Then, the ‘parameter’  page  page was switched

9.

Then the ‘valve’  was   was added from object palette the connection was set. At the ‘connection’   page, the settings were; inlet: 3 (stream 3) and outlet:4 (stream 4). The pressure pressure drop was set as 1.01 bar at the ‘parameter’  page   page on the design worksheet.

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10.

Then,two distillation column were added in stream 2 and stream 4 by clicked on the distillation column image on the “main case”.The overhead product in the top is distillate and the liquid is in the

11.

The project was saved and right-clicked at Environment: Case (main) which in steady mode,

12.

Finally, right clicked and clicked on add workbook table as have the energy stream, composition and material stream.The workbook also can be printed by clicked to the ‘tools’ , then choose ‘workbook’ and clicked on the ‘view’ button. On the Workbook-Case (main), right-clicked and ‘Print Datasheet’  was selected.

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THEORY

Distillation Distillation is a method of  separating mixtures   separating mixtures based on differences in volatility in  volatility of components in a boiling liquid mixture. Design and operation of a distillation tower depends on the feed f eed and desired products. Analytical method such as the McCabe-Thiele method can be used. A distillation tower needs more trays than the number of theoretical vapour-liquid equilibrium stages.

The McCabe-Thiele graphical method is considered as a basic and simple technique to determine the number of theoretical stages in a distillation column. However, it is demonstrated that there are a number of weaknesses in this method when it is used to the distillation of subcooled liquid (or superheated vapour) feed. There is also the problem of determining the optimum location of the feed stage in this graphical method.

The overall total and component material balance equations for a binary mixture distillation are as f ollows:

F=D+W F xF = D xD + W xW

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where F, D, W are feed, overhead, and bottom flow rates and x F, xD, xW  are the related compositions of the more volatile component of the binary mixture, respectively. respectively. The material balances over the enriching section of the column are:

V=L+D

 

      

By introducing the reflux ratio ,   ⁄ and knowing that

         



    

The equation becomes:

 

       

This is known as the equation of the operating line for the enriching section. Similarly, the material balances for the stripping section for the column are:

V’ = L’ – W

 

      

Equation above is the equation of the operating line for the stripping section. The feed types is characterized by using a factor q, defined as the number of moles of liquid flow in the stripping section that results from the introduction of each mole of feed.

q = (L’ - L)/F

or

L’ = L + qF

Similarly it can be shown that,

1-q = (V –  (V – V’ )/F or

V = V’ + (1 - q)F

In order to locate the intersection of the operating lines of the enriching and stripping sections, let yn+1 = ym+1 = y, xn = xm = x. Then, the equation becomes



      

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This is known as the equation of the feed line. The two operating lines and the feed line are plotted on the x-y diagram. The number of theoretical stages can be determined by using these lines and the equilibrium line.

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PROCESS FLOW DIAGRAM  Aspen Hysis Software

Figure 1: Process Flow Diagram for production of pure methanol

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4.0 WORKBOOK Table 1: Table for the material streams

Table 2: The composition of ammonia and water for each stream

Table 3: The energy stream

Condition

Pressure (bar)  Number of tray Feed tray Reflux ratio XD XB

Distillation column 1

Distillation column 2

5.2 16 12 1.26 0.96 0.04

1.01 13 9 0.834 0.96 0.04

Table 4: the information table about Distillation column 1 and Distillation column 2

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2.0

DISCUSSION The objective of this project is to understand the usage of valve and distillation

specification. The process involved is the production of methanol.. This process required one splitter, one valve and two distillation columns. The distillation column is used for dehydration to provide commercial methanol that is nearly free of water.

In this process, the feed of the methanol and water are considered an equimolar

mixture at 2700 kgmol/hr at 25˚C and 5.2 bar. The mole fractions of the feed mixture are 0.5 of methanol and 0.5 of water. It is then split into two stream and fed to two distillation columns, one at a reduced pressure and the other one at the same pressure. The amounts of the streams leaving the splitter have the same molar flowrate which is 1350 kgmol/hr. These two streams leaving the splitter is still in equimolar mixture. Valve is used in order to reduce the pressure to 1.01 bar before entering the second distillation column.

The stream 2 entering the DC1 is in liquid phase. There are two streams leaving the

DC1 which are bottom and distillate. The temperature at the distillate is 115.3˚C and t he temperature at the bottom is 145˚C while the pressure is still the same which is 5.2 bar  while in DC2 the pressure is reduce 1.01bar by using valve equipment. The temperature is different because of concept of distillation states that the separation of the mixture depends on the volatility of the components. Its means that the component with lower boiling point will vaporised first and going out at the distillate. In this case, methanol has the lower boiling point compared to water. Therefore, the product at the distillate is methanol which has 96% mole fraction while the remaining is water. At the bottom, water is the product and its mole fraction is 96% and the remaining 4% is methanol.

The stream 4 entering the DC2 is also in liquid phase. The temperature at the

distillate is 67.56˚C and the temperature at the bottom is 91.4˚C while the pressure is the reduce pressure which is 1.01 bar. The decrease in pressure will decrease the temperature. Even though the operating pressure for DC2 is difference with DC1, the composition of the product at distillate and bottom is also the same. Methanol is the desired product flowing out the distillate has the mole fraction of 96%. At the bottom of DC2, water is the product which is 96% mole fraction.

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 All the questions below are answered: answered:

1. What is the value of of the split ratio ratio for the feed feed stream for each DC? The value of the split ratio for the feed stream on DC1 is 0.5 and DC2 is 0.5

2. What is the molar molar flow in in stream before entering entering DC1? 1350 kgmole/hr

3. How to reduce pressure in DC2? The Valve equipment is added before DC2. The valve is t o reduce the pressure.

4. What is the temperature temperature at the bottom of DC1 and DC2? DC2?

The temperature of the bottom product in DC1 is 145 ˚C and DC2 is 91.4 ˚C

5. Did the process process achieve achieve a methanol methanol that free from water? What is the purity purity of the Methanol? Methanol? How to increase the purity?  Yes, The processes processes is achieved.The impurities impurities of the methanol which which are stated in commercial synthetic are acetone, formaldehyde .To increase the purity of the methanol by removing the impurities with the chemical method which is the formation of the resin.

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